The present invention relates to devices and methods for placement of ventriculoperitoneal shunts in human patients. More particularly, the present invention provides means for accurate and safe placement of ventriculoperitoneal shunts from a posterior approach.
Ventriculoperitoneal (VP) shunt placement for hydrocephalus is one of the most common procedures in neurological surgery. Hydrocephalus may result from subarachnoid hemorrhage, trauma, tumors, and the like. The technique entails introducing a catheter through brain tissue into one of the lateral ventricles of the brain. Cerebrospinal fluid in the ventricle may be vented through the catheter to relieve signs, symptoms, and sequelae of hydrocephalus.
The current surgical technique for placement of VP shunts was developed in the 1950's by Scarff and has persisted with few modifications. Despite the relative simplicity of this procedure, the complication rate can be significant and includes operative morbidity as well as post-operative infections, and obstructions, etc. Surgical technique plays a major role in reducing complications associated with VP shunts. Improper placement of the ventricular catheter may result in neurologic injury from the misplaced catheter or may cause an early proximal shunt obstruction, which is often secondary to blockage by adherent choroid plexus and other debris. The incidence of misplaced catheters is variable and dependent on a variety of factors, including the experience of the surgeon, the size of the targeted ventricle, the surgical approach and the use of intraoperative guidance, such as fluoroscopy, ultrasound, or endoscopy. Thus, to optimize shunt function and minimize morbidity proper placement of the proximal catheter is essential.
Two surgical approaches have been be used for VP shunt placement, frontal and parieto-occipital. Although little data is available, a retrospective series by Albright et al., J. Neurosurg. 69:883-886 (1988), found good catheter placement in only 55% of frontal shunts and 33% of parieto-occipital shunts. Four cases of ophthalmic injury following ventricular catheter insertion were reported recently and intracerebral hemorrhages secondary to misplacement have appeared in isolated clinical reports, but the rate of such complications is not known. Recently, endoscopic placement of ventricular catheters has been reported with an accurate placement rate of 90%. Neuroendoscopy: Volume 1, Mary Ann Liebert, New York, pp. 29-40 (1992). The disadvantages of this technique are related to the cost of the instrumentation, the added operative time, and the time required for the surgeon to become familiar with the technique. If, however, an accurate, rapid and inexpensive tool were available to aid in catheter placement, it would simplify the procedure.
A frontal catheter guide fulfilling these criteria has been successfully developed by Ghajar for placement of frontal ventricular catheters. Ghajar JB, J. Neurosurg. 68:318-319(1988). This instrument capitalized on the anatomical observation that a line passing perpendicular to the skull at the coronal suture will intersect the lateral ventricle.
However, parieto-occipital catheter placement has significant advantages over frontal catheter placement. The catheter path necessary for the frontal approach to the ventricles traverses frontal lobe regions having a low seizure threshold. Mechanical irritation of the neural tissue surrounding the catheter may give rise to epileptogenic foci independent of the underlying cause of hydrocephalus. This complicates patient management and increases health care cost, as well as markedly impacting the patient's quality of life.
The anatomy of the head and neck also cause technical difficulties for the surgeon. The distal end of the shunt is subcutaneously tunneled to the peritoneal cavity for implantation. Implantation in the open peritoneum provides an outlet for excess fluid drainage from the ventricles. The catheter path to the abdomen is circuitous from the frontal burr hole, however. The tube must pass posterior to the ear, and generally requires an additional skin incision. These difficulties increase operative time, cost, and complications.
What is needed in the art are devices and methods for accurate placement of VP shunt catheters by the parieto-occipital approach. The devices and methods should be easy for clinicians to learn and use. Optimally, expensive intra-operative imaging procedures should not be necessary. Quite surprisingly, the present invention fulfills these and other related needs.